Traceable calibration of non-linearities in laser interferometers

Laser interferometer systems are known for their high resolution, and especially for their high range /resolution ratio. In dimensional metrology laboratories, laser interferometers are popular workhorses for the calibration of measurement equipment. The uncertainty is usually limited to about 10 nm due to polarization- and frequency mixing. For demanding applications however nanometer uncertainty is desired. We present the measurements of interferometer components, which will be used to calculate an integral non-linearity by a virtual interferometer, of which the results will be verified with a traceable Fabry-Perot interferometer with sub-nm uncertainty.